Analysis And Correction Of The Images Acquired By IPC-208B Typed AFM

As one of the most important tools in nanoscale detection and nanoscale fabrication, AFM is receiving ever-increasing popularity in all kinds of application. The tunneling-current signals which acquired by AFM.IPC-208B,include both the sample's molecular structure and the dynamic characteristics of the whole AFM system .so the analysis of the AFM Image data become a all-important process.The main work in this thesis is to state the whole system of AFM.IPC-208B developed by Chongqing University, the effect factors to image quality is discussed, auto-correlation function (ACF) and power spectral density are employed to analyze the image data, then some improved suggestions and methods for image process and image enhancement are put forward.This thesis proposed and applied the analysis method for time-series signal to AFM image. The outline of this thesis is showed as follows:(1) the foundmental principles and the basic theories of AFM are introduced briefly, the effect factors to tested precision and image quality in the course of experiments is discussed, such as, cantilever tips'structure and the parameter settings.(2) The current methods of time-series signal analysis were reviewed. The advantages and disadvantages of several algorithms were introduced, such as, auto-correlation function (ACF), power spectral density (PSD), wavelet transform.(3) The auto-correlation function (ACF) and power spectral density (PSD) are utilized to analyze the signal acquired in several different scanning condition and the data's feature vector was extracted in both time space and frequency space. a damped harmonic oscillator model is presented. The general solution of such harmonic oscillator's Langevin equation is deduced . A good agreement on both ACF curve and PSD property is showed in comparing the fitting results with the experiment results. It could be concluded that the damped harmonic oscillator model are feasible for analyzing the dynamic characteristics of AFM system.(4) For the Down-Scanning mode of AFM.IPC-208B, a kinematics model of piezoceramics-sample-cantilever tip is applied, the sanning size error and cross-coupling error are analyzed, some approaches to minimize the errors are presented; At the sametime, a algorithm of AFM image real-time enhancement based on wavelet transform is proposed. Experients show that this method can remove noise,correct distortions and preserve significant details.